EE A SUPERVISOR WAS ASSISTING A FELLOW EE IN CHANGING A WATERLINE IN THE PREP -PLANT. HE WAS STANDING ON A LADDER AND AS THE WATERLINE BROKE LOOSE HE LOST BALLANCE AND FELL TO THE FLOOR LANDIN G ON HIS RIGHT FOOT. THE INCIDENT CAUSED A FRACTURE TO THE RIGHT HEEL. THE EE STARTED MISSING TIME ON 8-21-03 AND IS STILL UNDER THE DR. CARE AT THIS TIME.